Electric controlling apparatus



Feb. 6, 1940. F. G. LOGAN ELECTRIC CONTROLLING APPARATUS Filed Aug. 20,1936 2 Sheets-Sheet 1 INVENTOR l ke/1w 6'. lace/v J ATTORNEY 2Sheets-Sheet 2 F. G. LOGAN ELECTRIC CONTROLLING APPARATUS Filed Aug. 20,1936 INVENTOR fkA/wf 6. 1066 v M ATTORNEY nth-I:

Feb, 6, 1940.

Patented Feb. 6, 1940 ELECTRIC CONTROLLING APPARATUS Frank G. Logan,Mount Vernon, N. Y., assignor to Ward Leonard Electric Company, acorporation of New York Application August 20, 1936, Serial No. 96,967

@i. Iltl- 119) 18 Claims.

This invention relates to an improved con trolling apparatus and methodof control and is particularly applicable to changing the voltage Iapplied to a consumption circuit over a wide range, suchas in dimmercontrol oi lighting circuits in. theatres and the like. The invention isparticularly applicable to an auto-transformer connected to a supplycircuit and wherein the voltage applied to the consumption circuit is Qchanged by adjustment of the movable contact over the turns oiZ-theauto-transformer, although the invention is applicable also to variousinductive windings.

means for procuring any desired output voltage but their usehas beenlimited in practice to comv paratively small. capacity units on'accountof excesslve heating of the adjustable contact and of 20 the windings-oithe transformer when it is attempted-to increase the capacity beyondcomparatively small llmits.- When the usual movable contacting brush isused, it must necessarily engage adjacent turns oi? the transformerwinding and forms a short-circuit between them. The electromotive forceof the short-circulted turn or'turns tends to create a large current inthe short-circuited turn or turns and causes excessive heating in thewindings. In order to reduce 80 the value of the local current in thislocal shortcirculted path, the contacting brush has been made ofmaterial having a relatively high specific resistance for the purpose ofinterposlng in this .local circuit a suiliciently high resistance be-86' tween adjacent turns of the winding to reduce the value of the localcurrent and thereby reduce its heating effect. But the making of thebrush of high specific resistance material is incompatible with therequirement that the brush 40' be as of low a resistance as possible inorder to reduce the heating of the brush by the passage through it ofthe load current. This has necessitated resorting to a brush whichendeavors to effect a compromise between these twoantagonisticrequirements; and although such a compromise may beserviceable for auto-transformers of comparatively small capacity, theexcesslve heating in such brushes and in the windings of the transformerprevent their use for the control of voltage of the consumption circuitshaving comparatively large or heavy loads.

By the present invention the necessity for using a movable contact ofhigh specific resistance is avoided and the short-circuitlng of adjacentturns of the transformer winding is also 'The use of auto-transformerswith an adjustable contact affords a convenient and economicalavoidedwhich eliminates the excessive heating and heat losses above referredto. This invention thus permits the making of auto-transformers havingmovable contacts, of as high a capacity as may be desired without anyundue heating in the windings of the transformer or in the movablecontacts. This is accomplished by an improved relationship of themovable contact or contacts to the transformer winding in such a. mannerthat at no time does one contactbridge, or short-circuit, adjacent turnsof the winding. Other features of the invention in- I clude theprovision of reactors and also a discharge path in such relationship tothe movable contacts and to the load circuit that no material arcingoccurs in moving the contacts along the transformer winding and noobjectionable heat losses or drop in volts occurs in the load circuit.

One object of.the invention is to provide an 20 improved form ofadjustable auto-transformer adapted to be made for any desired capacity.Another object is to provide such a transformer which will permit theuse of contact brushes of high conductivity and avoid the heating due toshort-circuiting of the windings and avoid undue heating in the movablecontacts. Another object is to provide an improved form of device forcontrolling the voltage of the load circuit over a wide rangeeconomically and without high heat losses. Another object is to increasethe number of steps of voltage control beyond the number of conductiveportions of the winding engaged by the movable contact or contacts.Other objects and advantages of the invention will be understood fromthe following description and accompanying drawings.

Fig. l is a diagram and plan view of a portion of the apparatusillustrating one embodiment of the invention; Fig. 2 is a side view ofone form of structure embodying the invention; 40 Fig. 3 is an end viewthereof; Fig. 4 15a plan view; and Fig. 5 is a bottom view of thecontact carrier.

Referring to Fig. 1, an alternating current source I supplies energythrough the auto-trans- 45 former to the load circuit 2, indicated as alamp circuit, although the load may be of any character. The transformeris indicated for simplicity as having a straight iron core 3 upon whichis wound the winding 4. The turns of this winding are indicated asphysical turns of wire of a comparatively large size and wouldordinarily be provided withan insulating covering except at certainexposed portions. The connections to this winding and to the source andto the load and throughthe reactors are indicated as single lines inconventional diagrammatic form. At opposite sides of the winding andcovering alternate turns thereof are indicated a series of insulatingstrips 6. The turns of the windings between these strips are flush withthe surface of the outside of these strips and have their conductiveportions exposed in line with the outside portions of the strips. Thatis, considering the conductor of the winding at the right-hand end ofthe transformer, this conductor passes from a connection to the source Iunder the core and up the front side of the-core under an insulatinstrip 5 and then oven and down the rear side 01' the core where itsouter conducting surface is exposed and then passes under the core andup at the front side of the core where its outer conducting surface isexposed. It then passes over the core and down the rear side under aninsulating strip 5 and then under the core and up the front side underan insulating strip 5. This sequence of turns and relationship of theadjoining turns on the two sides of the core 3 continues throughout thelength of the winding to its opposite end where it is connected to theother terminal of the source I. It is evident that if a movable contactbe moved over the rear side of the winding from right to left, orviceversa, it will first engage and make contact with an exposed portionof a turn pi' the winding and then with an insulating strip, then makecon.- nection with another turn and then. contact with an insulatingstrip andso on. If a; movable contact be passed along th'e-fmnt'side ofthe winding, it will similarly make contact first with an insulatingstrip, then with'one turn of the winding. then with an insulating stripand then make conductive connection with the next turn of the windingand so on, it .being understood that the insulation along the paths ofthe movahle contacts has been removed from the outer surface of thewinding to permit the movable contacts to electrically engage the turnsbetween the insulating strips. It follows that in this construction amovable contact on one side will successively engage every other turn ofthe winding and completely break connection with the winding whilepassing over the insulating strips, provided the width of the movablecontact or brush is less than the width of the insulating strips 5.Asimilar brush on the other side of the winding will successively engageevery other turn of the winding and break connection when passing overthe strips 5.

In Fig. 1 two movable contacts or brushes 8. 6a are shown on oppositesides of the winding and these are mechanically related in fixedposition to each other so that when one brush, for example brush 8, ismaking complete electrical connection with one turn of the winding, theother brush 6a is making complete engagement with one of the insulatingstrips and is therefore not connected to the winding at all. If now thetwo brushes be simultaneously moved slightly to the right so as to beover the joints between the insulating strips and the turns, of thewinding, then brush 6 will partially engage one turn of the winding andbrush Ba will partially engage the same turn of the winding at the otherside thereof. Further movement of the brushes to the right will causebrush 8 to be wholly on an insulating strip and cause brush to to bewholly on a turn of the winding in the positions indicated by dottedlines. Upon further movement to the right both brushes will partiallyengage insulating strips and partially engage a. turn of the windings;and further movement will cause the brush 8 to wholly engage a turn ofhe winding while brush 6a wholly engages an insulating strip, takingpositions corresponding to those shown in full lines in Fig. 1. It willthus be seen that as these brushes are simultaneously moved along theirpaths, first brush 6 engages a turn of the winding while the brush 6a isdisconnected therefrom, then both brushes partially engage a turn andinsulating strips, giving a condition under which both brushes engagethe winding with half a turn difference between them, and then brush 6awholly engages a turn of the winding while brush 8 is disconnectedtherefrom and so on. I

Brush 6 is connected through a reactor winding 1 to the conductor 8which leads to the consumption circuit, while brush 6a is connectedthrough .a reactor winding la to the conductor 8. An impedance device 9which may be a noninductive resistance, is connected from a pointbetween the brush 6: and the reactor winding 1 to a point between thebrush 6aand the reactor winding 1a.

;-- It is evident th-at in the above-analysis, of

the circuit changes accomplished by the movement of the brushes '6 andto, that in the position shown with brush 6 engaging a turn of thewinding and the brush 6a insulated from the winding, the full loadcurrent will pass from the source I through the left-hand portion of thetransformer'- winding to the brush 6 then through reactor! and conductor8 to the load and then from the load back to the source i. When thebrushes are bridging portions of insulating strips and portions of aturn of the winding, current will pass from the source I through theleft-hand portion of the transformer winding to both brushes,approximately half of the current passing through brush 6 and reactor tothe conductor 8 and the other approximate half of the current passingthrough brush 6a and reactor 1a to conductor 8 in parallel and thenthrough the load back to the source I. Further movement to increase thevoltage sup-- plied to the load results in brush 5 wholly engaging aninsulating strip while brush to wholly engages a turn of the winding.Current then hand portion of the transformer winding to brush 6a andthen through reactor la and conductor 8 to the load and then back to thesource. This sequence of changes of current paths takes place as thebrushes are moved throughout the length of the transformer winding 'ineither direction when changing the voltage supplied to the consumptioncircuit.

It will be appreciated that when the movable contacts 6 and 6a are inbridging positions and engaging the same turn of the winding at pointsone-half turn apart, there is an electromotive force due to such halfturn imposed upon the local circuit from one brush through the tworeactor windings in series back to the other brush. This causes a localexciting current to pass through the reactor windings which howeverserve as chokes to limit the value of this exciting current. The numberof turns of the reactor windings and the cross-section area of the coresof these windings are designed such as to limit .this exciting currentto a desired minimum the iron of the cores at or near the knee of themagnetization curve. Under such conditions although approximatelyone-half of the load current is also passing through each oi the reactorwindings, the increase in magnetization of the iron due to the loadcurrent is comparatively small and consequently the drop in volts due tothe efi'ect of the reactors upon the load circuit is not increased toany objectionable amount. Similarly when only one brush is in engagementwith the transformer winding and one reactor only is conducting the fullload current, the magnetization of the core of this reactor is notappreciably increased beyond the knee of the magnetization curve andconsequently the drop in volts due to the comparatively small reactanceof this reactor with reference to the full load current is limited to anunobjectionable amount.

It is thus apparent that the reactors in the local circuit between thebrushes serve to limit the local exciting current to an amount which maybe made comparatively small so that there is no undue heating of thewindings of the transformer and that these reactors may be designed sothat the drop in volts as regards the load circuit is not objectionableand that the reactors may be located apart from the transformer windsing so that any heating of the reactors does not affect the heating ofthe transformer winding or of the contacting brushes. It will likewisebe evident that since the movable contacts do not bridge adjacent turnsof the transformer winding, there is no necessity for making them ofhigh specific resistance material. They may therefore be made of metalof the highest conductivity such as copper which permits excellentconductive engagement with the turns oi the transformer winding andheating of the movable contacts or brushes is avoided. Thusthe'objections which limit the use of adjustable autotransformers tounits of comparatively small capacity when brushes of high specificresistance material are used, causing excessive heating of thecontacting parts and of the transformer windings, are entirely overcome.

In passing from a condition where one contact makes sole connection withthe winding to the condition where the other contact makes soleconnection with the winding,- the intermediate condition of jointconnection to the winding by both contacts gives an additional step ofvoltage control over that obtained with the usual type ofauto-transformer and thereby doubles the number of voltage control stepsover that obtained in the usual. type, because the joint condition ofcontact provides additional steps by reason of the provision of thereactors. If, however, the voltage drop due to the load current in thereactors is permitted to be undesirably high, the control voltage inpassing through successive steps" would be irregular. In order to obtaina progressive increase or a progressive decrease in the control voltagein each step, the number of turns of the reactor windings and thecross-sectional area of the cores of these windings are designed notonly to limit the exciting current to a desired minimum amount, but theparts are preferably proportioned to cause the exciting current to bringthe magnetization of the cores at or near the knee of the magnetizationcurve.

as already explained. This will ordinarily reduce the drop in thereactor windings to such value that an increase or a decrease of thecontrolled voltage is obtained in passing through each successive stagein the movement of the contacts. In order to obtain this result the dropin volts in each reactor when carrying the full load current should beless than the voltage across adjacent conducting portions of thetransformer winding in the path of one of the contacts; and moreuniformity oi control is obtained in passing through successive stepsthe smaller the drop in volts due to the load current in the reactors.However, as above explained suiiicient reactance must be provided toinsure proper limitation of the current in the local circuit through thereactors when the contacts are in joint connection with two portions ofthe winding.

The shunting impedance 8 in this form of construction provides adischarge path between its points of connection and serves not only toavoid any tendency to arcing at the movable contacts when interruptingconnection with a turn of the transformer winding but also serves topermit a discharge current to pass from the reactor which is beingdisconnected from the load circuit to permit the core of this reactor toapproach the condition of non-magnetization in case the interruption ofthe circuit is made at a pear or near a peak of the alternatingmagnetization. Thus when the adjustable contacts are moved to cause there-establishment of the current through this reactor, the iron has inthe meantime been conditioned to a point considerably below the peak ofmagnetization, resulting in a reduction of excessive or undesirabletransient current conditions.

In prior practice, two adjustable contacts have been connected throughan inductive reactor having a common core and using a mid-tap for thecircuit connection. Ii such a device were substituted for the reactors iand 1a of the present improvement and ii the impedance or resistor 5were eliminated, the result would be that when contact 6 was inconnection with the winding and contact to on'an insulating strip, avoltage would be built up from the center tap to the contact 8a whichwould be a function of the passing load current. Also the polarity ofthis voltage would be reversed with respect to the polarity of the turnwith which it will next come in contact. This would result in excessivearcing and sparking, as has been found to be the case in practice. Theuse of individual or independent inductive reactors together with theshunt resistor 9 gives a very great advantage over the prior tappedinductive reactor. For example, when the contacts 6 and Ba are movedfrom a position where they both engage the winding 4 to a position wherecontact 8a is on an insulating strip, the iron of the reactor 1a mayhave been left at any point on its magnetization curve. However,although full load current is now passing through reactor '5, itsmagnetization can have no effect upon reactor Ia, which is quitedifferent from the condition when a tapped reactor having a common coreis used. The impedance or resistor 9 of the present improvement nowpermits the flux in the core of reactor la to collapse and permits theiron to return to a condition at or near zero magnetization. Thus whencontact la nemt engages an adjacent turn The transformer is shown ashaving two hori-- zontally extending legs l joined by crosspieces H atthen ends. The transformer winding is made up of one portion l2 on theupper leg, the turns of which are adapted to be adjustably engaged bythe movable contacts; and a few turns l2 cf the winding are shownenveloping one end of the lower leg of the core, as it is oftenunnecessary to cut out all of the transformer winding Irom the circuit.The winding I2 instead of being engaged on opposite sides as indicatedin Fig. 1, is arranged to have both contract devices engage the windingon. its top surface. The two paths of contact engagement are each formedof a contacting portion of the winding and then a non-electricalcontacting portion over the adjacent turn of the winding and then anexposed contacting portion over the next turn of the winding and so on.That is, referring to the lead l3 at the left-hand corner of Fig. 2,this is shown passing under and aroundthe rear side of the core andthen, as shown in Fig. 4, it passes under an insulating strip I4 on thetop of the core for about half its length and then rises to formanexposed contacting portion i5, and then" passes down andflaround thecore and up on the rear side of the core and then forms anexposed'contacting portion l5a. on the top of the core for aboutnh'alfthe width of the core and then under an insulating strip Ha for abouthalf the width of the top of the core. .lhe winding then continuesaround the core and up on the rear side where it first passes under aninsulating strip i i and then forms an exposed portion i5 and so onthroughout the length of the winding i2. It is thus evident that when acontact passes along one or these paths, it will alternately contactelectrically with a portion of the winding, then pass over anon-conducting space represented by an insulating strip covering thenext turn of the winding and then engage a contacting portion of thewinding and so on.

This relationship of electrical contacting portions and non-contactingportions may conveniently be constructed by forming a moulded strip ofinsulating material, such as Bakelite. Such a strip would have a topsurface wherein along one path are located alternate depressed andraised portions extending crosswise and a similar path on the remaininghalf of the top surface with the depressed and raised portions staggeredwith reference to the similar portions of the other half. That is, wherethe winding passes under the strip l4 there is a slot in the insulatingstrip [6 as shown at 16a in Fig. 3. and opposite this slot is locatedthe raised portion 5b of the insulating strip over which the portion l5of the winding passes as shown in Fig. 3. The next turn of the windingpasses over .a raised portion corresponding to l6b which is located atthe right-hand side of Fig. 3 and then down into a slot corresponding to|6a which is located at the left-hand side of Fig. 3. After the windingis thus formed on the insulating strip and on the core of thetransformer the insulating strips corresponding to M, Ma,

and lb are inserted over the depressed portions of the winding, as shownin Fig. 3. After the structure is thus formed, insulating varnish may beapplied to cover the parts and then be heat treated to cure thevarnishand Bakelite to form a solid, strong, firm structure. Thetopsurface of the unit is then smoothed oil in a surface grinder toobtain smootkpaths for the movable contacts to travel over. Thisgrinding and smoothing operation will remove the insulation from the topsurface of the winding so that e1ectrical connection may be madetherewith by the movable contacts. A winding having a condor tor ofsquare orv rectangular cross-section Will be found most convenientforforming the structure and in giving a suitable exposed contact surfacewhere the insulation is removed. It is evident that instead of havingone turn only between successive electrical contacting portions of thewinding, a number of turns may be provided where desired and built up ineach depressed portion and over each raised portion of the insulatingstrip i6, in which case the turns will preferably be banked to'bring theexposed contacting portion at the top. This relationship of electricalcontacting portions and non-electrical contacting portions in two pathsmay, of course, be formed in other ways.

Although movable contacts in the form of brushes of high conductivematerial might be used in some cases, a,structure using rollers as themovable contacts is shown in Figs. 3 to 5, as they are, when properlyconstructed and mounted, more certain to give and maintain uniformity ofcontact with the winding and avoid the possibility of minute arcs whichmight occur with the use of brushes owing to possible irregularity ofcontact. The avoidance of arcing, of course, is desirable as itpermitsthe contacting portions to maintain smooth contacting surfaces andinsures continuance of good contact at all times and in all portions ofthe parts. Although one contact roller might be used for engaging eachpath of the winding in theory, the irregularities of manufacture make itdesirable to use two rollers for engaging each path with one slightlydisplaced with reference to the other.

The rollers theoretically make a line contact with the contactingportions of the windings and the distance between the line contactsofthe two rollers in a direction at right angles to the line contactshould be less than the width of the insulating strips M, a, etc. Inpractice it is desirable to make this relative displacement of thebrushes equal toabout one-half of the width of these insulating strips.

The contact rollers are mounted upon a carrier formed of an insulatingplate I! which serves as a support for the rollers. Each of .the rollersi8a, I81), I80 and Net is rotatably mounted between two ears I9depending from metal strips Illa. These strips extend in a lengthwisedirection with reference to the core and are each loosely supported attheir inner ends by a downwardly extending post 20 which is fixed at itsupper end to the insulating plate I! and is provided with a pin 20a atits lower end which passes loosely through an opening in the end of thestrip I911. The other end of each strip is guided by a post 2|, as shownin Fig. 2, which is fixed at its upper end to the insulating plate H,the lower end passing loosely through an opening in one end of the stripl9a. A spring 22 encircles each post 2| and seats at its upper endagainst the underside of the plate I1, the lower end seating against theupper surface of the strip i9a. Each strip is shown of U-form at itsleft-hand end in order to conveniently accommodate the reception of thepast 2| and spring 22 as shown. It is evident that the spring 22 Yexerts a downward pressure on one end of the strip Na and thereby forcesthe contact roller with a uniform pressure into engagement with the topportion of the transformer winding, the post and pin 20a serving toguide and support the other end of the strip lfla.

The contact rollers or wheels are made of copper to give good electricalcontact and to avoid heating and are tightly fixed upon hubs 23 made ofcopper graphite composition to provide an anti-friction bearing on thesupporting steel axle carried by the ears l9. These hubs form'a goodelectrical connection with their supporting axles, the axles being fixedto the depending ears l9. trical contact with the rollers and from eachend of these strips flexible copper leads 24 and 24a are connected toblocks or contact shoes 25 and 25a. These shoes are mounted on top ofthe insulating plate I! and are located at each of its corners. The pairof shoes 25 and 25a on one side of the plate I! are in electricalconnection by the flexible leads 24 and 24a with the two rollers 18c andI8d which engage One path of alternate contacting and non-contactingportions of the winding. The two shoes 25 and 25a on the other side ofthe plate I! are in electrical connection with the two rollers |8a and[8b which engage the other path of alternate contacting andnon-contacting portions of the winding. Furthermore, as shown in Fig. 5,one roller of each pair is advanced slightly with reference to the otherroller of its pair for securing the displacement of line contact of thetwo rollers so that the distance between their lines of contact in adirection at right angles thereto will be less than the width of theinsulating strips H, a, etc. This displacement is accomplished byslightly offsetting the mounting of the strips lid on the insulatingplate IT, as shown in Fig. 5.

At each end of the core is clamped, by the end plates 26, the lower endsof an inverted U-shaped strip 21. Above the transformer core andextending longitudinally therewith is a pair of contact rails preferablymade of brass and which are of angular form as shown in Fig. 3. The endsof these rails extend within the upper portion of the inverted U-strips21 and are fixed thereto by bolts 3|, intervening insulation material 32being interposed between these rails and the U-supports 21, the boltslikewise being insulated from the supports 21 by insulating washers 33and the shank of these bolts being likewise insulated from the supports21. The top surface and outer sides of the contact shoes 25 and 250 arein sliding contact with the inside surfaces of the two angle rails 30respectively, as well shown in Fig. 3. It is therefore evident that thecurrent from the two pairs of rollers is conducted respectively to thetwo conducting rails 20.

Referring to Fig. 2 it will be seenthat one of the end clamping plates26 of the core is extended and forms an outwardly extending flange 35.On the outer face of this is mounted an insulating strip 36 on which aremounted three terminal bolts 31a, 31b and 310. These bolts are of courseinsulated from the supporting flange 35. connection is made to theterminal 31a from one end of the portion [2 of the transformer winding,as shown in Fig. 2. Connection to the terminal 31b is made to the otherend of the transformer winding as shown by the lead I; in Fig. 2. Thetwo terminals 31a and 31b are connected to the source of energy, such asthe source I of Fig. 1. The terminal 31c is connected to one side of theconsumption circuit by a conductor which corresponds to the lead 8 ofFig. 1.

Secured to the upper portions of the sides of The strips 19a are thus ingood electhe left-hand U-support 21 are strips 40 which extend to theleft and have outwardly projecting flanges, as shown in Figs. 2 and 4.The front pair of flanges support the iron core 4| of a reactor having awinding a. The flanges 40 at the rear side of the unit support a similarcore 42 of a reactor having a winding 42a. The lead 43 from the rearterminal bolt 3i is connected to one terminal of the reactor winding 42athereby placing this winding in electrical connection with the rear rail30 and the rear pair of brushes. A lead 44 from the other terminal ofthis winding is connected to the upper terminal 310. A lead 45 from thefront terminal bolt 3! is connected to one terminal of the reactorwinding a, thus placing it in electrical connection with the front pairof brushes. The other terminal of this winding is connected to theterminal 31c by a lead 46, thus bringing the terminals of the reactorwindings to a common connection from which the lead 8 of Fig. 1 extendsto one side of the consumption circuit. A point in the lead 43 isconnected to one terminal of the impedance or resistive device 8a, theother terminal of which is connected to a point in the lead 45, thusforming a discharge path connection between these points correspondingto the discharge path provided by the impedance 8 as shown in Fig. 1.

In order to move the carrier assembly over the two paths of thetransformer winding, a handle or any other convenient means may beprovided. In the drawings a yoke is shown pivotally mounted at a fixedpoint 5| below the unit and having the sides of the yoke extendingupwardly and embracing the two sides of the unit. The upper ends of theyoke are slotted to engage a pair of rollers 52 which arerotatably'mounted on pins 53 formed on the ends of a square rod which issecured to the underside of the insulating plate I1 and extendingcrosswise thereto. The controlling yoke is provided with a handle 54below the pivot 5| and it is evident by moving the handie, the contactcarrier assembly may be moved along to any position desired foradjustment of the voltage applied to the load circuit. Instead ofproviding an operating handle 54, this part may be connected to otheroperating means for securing control as desired in relationship to othercontrolling devices and arranged for obtaining presets of lightingscenes and graduation of control in a manner which will be understood bythose skilled in the art. It will be appreciated that the springs 2| notonly serve to press the contacting rollers or wheels into properengagement with the contact portions of the transformer winding but alsoserve to force the contact shoes 25 and 25a upwardly into engagementwith the angle rails 30, thus securing and maintaining good electricalcontact in all positions of adjustment.

The operation of the structure shown in Figs. 2 to 5 will be understoodfrom the description already given in connection with Fig. 1. However,by reason of the two paths of travel of the contacts being on the topside of the transformer winding in Figs. 2 to 5, as distinguished frombeing on two opposite sides as indicated in Fig. 1, it will beappreciated that when the rollers are in bridging position betweencontacting portions of the transformer winding and adjoining insulatingstrips, one turn of the transformer winding is in series with thereactive devices in the local circuit, as distinguished from a half turnunder the same conditions in Fig. 1.

Where the claims refer to the inductive reactive devices as havingindividual iron cores, it should be understood that this means the fluxof each of the cores isnot materially aflected by.

i1,-. Electric controlling apparatus comprisin an inductive windinghaving alternate exposed electrical contacting portions of the windingwith intermediate non-electrical contacting portions in a path along thewinding and other alternate exposed contacting portions or the'windingwith intermediate non-contacting portions in another path along thewinding, contacts movable along said paths respectively, means forcontinuously maintaining said contacts in the same relative position toeach other at all times including the time of simultaneous movementalong said paths, longitudinal conductors extending over said pathsrespectively, and means for maintaining electrical connection between.

said contacts and said conductors respectively when said contacts aremoved along said paths.

2. Electric controlling apparatus comprising an inductive winding havingalternate exposed electrical contacting portions of the winding withintermediate non-electrical contacting portions in a path along thewinding and other alternate exposed contacting portions of the windingwith intermediate non-contacting portions in another path along thewinding, contacts movable along said paths respectively, means forcontinuously maintaining said contacts in the same relative position toeach other at all times including the time of simultaneous movementalong said paths, longitudinal conductors extending over said pathsrespectively, contacts engaging said conductors and electricallyconnected with said first named r ies'with each or said contactsrespectively and connected between said contacts and said com- 'monconnection, said reactive devices being proportioned to cause theircores to be magnetized approximately in the region of the knee of themagnetization curve when they are jointly connected in the load. circuitand to be magnetized beyond the knee of the curve when individuallyconnected in the load circuit.

5. Electric controlling apparatus comprising an adjustable inductivewinding, contacts electrically connected to each other and having acommon connection to a load circuit and adapted 'to be alternatelyconnected to said winding and to be jointly connected tosaid windingbetween the alternate connections, an individual iron cored inductivereactive device connected in series with each of said contactsrespectively and connected between said contacts and said commonconnection, said reactive devices being proper tioned to cause theircores to be magnetized approximately in the region of the knee of themagnetization curve when they are jointly connected in the load circuitand to be magnetized beyond the knee of the curve when individuallyconnected in the load circuit, and an impedance device connected irom apoint between one of said contacts and its reactive device to a pointbetween the other oi said contacts and its reactive device.

contacts respectively, and means for yieldably forcing said first namedcontacts in one direction into engagement with their respective pathsand for yieldably forcing said second named contacts in the oppositedirection in engagement with their respective conductors.

3. Electric controlling apparatus comprising an adjustable inductivewinding, contacts electrically connected to each other and variablyconnected to said winding and having a common connection to a loadcircuit. an individual iron cored inductive reactive device connected inseries with each of said contacts respectively and connected betweensaid contacts-and said common connection, said reactive devices beingproportioned to cause their cores to be maintained at approximatesaturation under all operating conditions, and an impedance deviceconnected from a point between one of said contacts and its reactivedevice to a point between the other of said contacts and its reactivedevice. 1 4. Electric controlling apparatus comprising an adjustableinductive winding, contacts electrically connected to each other andhaving a common connection to a load circuit and adapted to bealternately connected to said winding and to be Jointly connected tosaid winding betweenthe alternate connections, and an individual ironcored inductive reactive device connected in seintermediatenon-electrical contacting portions in a path along the winding and otheralternate exposed contacting portions of the winding with intermediatenon-contacting portions in another path along the winding, contactspermanently electrically connected to each other and movable along saidpaths respectively, and means for continuously maintaining said contactsin the same relative position to each other at all times including thetime of their simultaneous movement along said paths and for maintainingan offset electrical contact condition between one of said contacts andits path and that of the other of saitd contacts and its path when movedalong said pa hs.

7. Electric controlling apparatus comprising an inductive winding havingalternate exposed electrical contacting portions of the winding withintermediate non-electrical contacting portions in a path along thewinding and other alternate exposed contacting portions of the windingwith intermediate non-contacting portions in another path along thewinding, contacts permanently electrically connected to each other andmovable along said paths respectively and having a common connection toa load circuit, an individual iron cored inductive reactive devicepermanently connected in series with each of said contacts respectivelyand permanently connected between said contacts and said commonconnection, and means for continuously maintaining said contacts in thesame relative position to each other at all times including the time 01their simultaneous movement along" said exposed contacting portions ofthe winding with intermediate non-contacting portions in another pathalong the winding, contacts electrically connected to each other andmovable along said paths respectively and having a common connection toa load circuit, an individual iron cored inductive reactive devicepermanently connected in series with each of said contacts respectivelyand permanently connected between said contacts and said commonconnection, an impedance device connected from a point between one ofsaid contacts and its reactive device to a point between the other ofsaid contacts and its reactive device, and means for maintaining saidcontacts in fixed mechanical relation to each other for alternately andjointly making engagement with said contacting portions of therespective paths when moved along said paths.

9. Electric controlling apparatus comprising an inductive winding havingalternate exposed electrical contacting portions of the winding withintermediate non-electrical contacting portions in a path along thewinding and other alternate exposed contacting portions of the windingwith intermediate non-contacting portions in another path along thewinding, contacts permanently electrically connected to each other andmovable along said paths respectively, the contacting portions of saidcontacts in the direction of movement having a width less than the spacebetween the contacting portions of said winding, and means forcontinuously maintaining said contacts in the same relative position toeach other at all times including the time of their simultaneousmovement along said paths and for alternately making engagement withsaid contacting portions of the respective paths when moved along saidpaths.

10. Electric controlling apparatus comprising an inductive windinghaving alternate exposed electrical contacting portions of the windingwith intermediate non-electrical contacting portions in a path along thewinding and other alternate exposed contacting portions of the windingwith intermediate non-contacting portions in another path along thewinding, contacts permanently electrically connected to each other andmovable along said paths respectively and having a common connectionto aload circuit, the contacting portions of said contacts in the directionof movement having a width less than the space between the contactingportions of said winding, an individual iron cored inductive reactivedevice per manently connected in series with each of said contactsrespectively and permanently connected between said contacts and saidcommon connecion, and means for continuously maintaining said contactsin the same relative position to each other at all times including thetime of their simultaneous movement along said paths and for alternatelyand jointly making engagement with said contacting portions of therespective paths when moved along said paths.

11. Electric controlling apparatus comprising an inductive windinghaving alternate-exposed electrical contacting portions of the windingwith intermediate non-electrical contacting portions in a path along thewinding and other alternate exposed contacting portions of the windingwith intermediate non-contacting portions in another path along thewinding, contacts electrically connected to each other and movable alongsaid paths respectively and having a common connection to a loadcircuit, the contacting portions of said contacts in the direction ormovement having a width less than the space between the contactingportions of said winding, an individual iron cored inductive reactivedevice permanently connected in series with each of said contactsrespectively and permanently connected between said contacts and saidcommon connection, an impedance device connected from a point betweenone of said contacts and its reactive device to a point between theother of said contacts and its reactive device, and means formaintaining said contacts in fixed mechanical relation to each other foralternately and jointly making engagement with said contacting portionsor the respective paths when moved along said paths.

12. Electric controlling apparatus comprising an inductive windinghaving alternate exposed electrical contacting portions of the windingwith intermediate non-electrical contacting portions in a path along thewinding and other alternate exposed contacting portions of the windingwith intermediate non-contacting portions in another path along thewinding, contacts movable along said paths respectively, means forcontinuously maintaining said contacts in the same relative position toeach other at all times including the time of their simultaneousmovement along said paths, and conductors permanently electricallyconnected together extending in a direction parallel with said pathsrespectively and in electrical connection with said contactsrespectively.

13. Electric controlling apparatus comprising an inductive windinghaving alternate exposed electrical contacting portions of the windingwith intermediate non-electrical contacting portions in a path along thewinding and other alternate exposed contacting portions of the windingwith intermediate non-contacting portions in another path along thewinding, contacts movable along said paths respectively, conductorspermanentlyelectrically connected together extending in a directionparallel with said paths respectively and in: electrical connection withsaid contacts respectively, said conductors having a common connectionto a load circuit, an individual iron cored inductive reactive devicepermanently connected in series with each of said conductorsrespectively and permanently connected between said conductors and saidcommon connection, and means for continuously maintaining said contactsin the same relative position to each other at all times including thetime of their simultaneous movement along said paths and for alternatelyand Jointly making engagement with said contacting portions of therespective paths when moved along said paths.

14. Electric controlling apparatus comprising an inductive windinghaving alternate exposed electrical contacting portions oi the windingwith intermediate non-electrical contacting portions in a path along thewinding and other alternate exposed contacting portions of the windingwith intermediate non-contacting portions in another path along thewinding, contacts permanently electrically connected to each other andmovable along said paths respectively, said paths being located adjacentto each other, and means for continuously maintaining said contacts inthe same relative position to each other at all times including the timeof their simultaneous movement along said paths and for maintaining anoflset electrical contact condition between one 01 said contacts and itspath and that of the other 0! said contacts and its path when movedalong said paths.

15. Electric controlling apparatus cmnprising 16 electrical contactingportions 01 the winding with intermediate non-electrical contactingportions in a path along the winding and other alternate,"

exposed contacting portions of the winding with intermediatenon-contacting portions in another path along the winding, contactspermanently electrically connected to each other and movable along saidpaths respectively, one of said paths being located on one side of saidwinding and the other of said paths being located on another side ofsaid winding, and means for continuously maintaining said contacts inthe same relative position to each other at all times including the timeof their simultaneous movement along said paths and for maintaining anofiset electrical contact condition between one or said contacts and itspath and that of the other of said contacts and its path when movedalong said paths.

16. Electric controlling apparatus comprising an inductive windinghaving alternate exposed electrical contacting portions of the windingwith intermediate non-electrical contacting portions in a path along thewinding and other alternate exposed contacting portions of the windingwith intermediate non-contacting portions in another path along' thewinding, contactspermanently electrically connected to each other andmovable along said paths respectively, each 01' said paths comprisingalternate raised and depressed portions of the winding and insulatingmaterial covering said depressed portions to provide smooth contactingsurfaces for engagement by said contacts, each raised portion in onepath and depressed portion in the other path forming portions of thesame turn of the winding, and means for maintaining saidcontacts-infixed mechanical relation to each other for maintaining an offsetelectrical contact condition between one of said I contacts and its pathand that of the other of said contacts and its path when moved alongsaid paths.

17. Electric controlling apparatus comprising an inductive windinghaving alternate exposed electrical contacting portions 01' the windingwith ,intermediate non-electrical contacting portions f in'a path alongthe winding and other alternate exposed contacting portions oi. thewinding ,with intermediate non-contacting portions in another path alongthe winding, contacts permanently electrically connected to each otherand movable along said paths respectively, each of said paths comprisingalternate raised and depressed portions of the winding and insulatingmaterial covering said depressed portions to provide smooth contactingsurfaces for engagement bysaid contacts, each raised portion in one pathand depressed portion in the other path forming portions of the sameturn of the winding, and the raised and depressed portions in one pathof said winding being in staggered relation to the raised and depressedportions of the winding of the other path. and means for maintainingsaid contacts in fixed mechanical relation to each other for maintainingan oii'set electrical contact condition between one of said contacts andits path and that of the other of said contacts and its path when movedalong said paths.

18. Electric controlling apparatus comprising an adjustable inductivewinding, contacts electically connected to each other and variablyconnected to said winding and having a common connection to a loadcircuit, an individual iron cored inductive reactive device permanentlyconnected in series wtiheach or said contacts respectively andpermanently connected between said contacts and said common connection,said reactive devices being proportioned to cause their cores to bemaintained at approximate saturation under all operating conditions,andmeans for continuously maintaining said contacts in the same relativeposition to each other at all times including the time of theirsimultaneous movement for alternately and Jointly making engagement withsaid'winding when moved to make a variable connection to said winding.

FRANK G. LOGAN.

